Recently, a semiconductor device using silicon carbide (SiC) (referred to as “the silicon carbide semiconductor device” hereinafter) attracts attention as a next-generation semiconductor device capable of achieving a high withstand voltage and low loss. Since a dielectric breakdown electrical field strength of SiC is approximately 10 times as large as that of silicon (Si) which has been used for a conventional semiconductor device, particularly expected is a development of the silicon carbide semiconductor device to a high withstand voltage power semiconductor device.
It is known that in the silicon carbide semiconductor device, in order to further enhance the withstand voltage, a p-type guard ring region (a terminal well region) is provided in a so-called terminal region (a terminal part) in an n-type silicon carbide semiconductor layer to reduce an electrical field caused by a reverse voltage by a depletion layer which is formed by a PN junction between the silicon carbide semiconductor layer and the guard ring region (for example, Patent Document 1). Moreover, in a Schottky barrier diode made of SiC (SiC-SBD, SiC-Schottky Barrier Diode) described in Patent Document 1, an interlayer dielectric film (a field insulating film) is provided on the silicon carbide semiconductor layer in the terminal region, and an outer peripheral edge of a surface electrode is formed to extend onto the interlayer dielectric film. Furthermore, polyimide is formed as a protective film to cover part of the surface electrode and the interlayer dielectric film.